One consequence of the recent development of higher-output engines is that the repulsive force generated by the clutch springs has become much greater, so that the effort required to operate the clutch pedal has increased correspondingly. Not surprisingly, there is now considerable demand for an apparatus able to provide the maximum reduction possible in the pedal effort.
In conventional pedal effort-reduction apparatuses, a torsion coil spring is used as the means for urging the pedal. One such apparatus is disclosed in Japanese Utility Model Disclosure No. 62-18720.
In this prior art apparatus, a horizontal support shaft is attached to a support bracket, and the support shaft is fixed to a car body. A movable pedal arm is mounted on the shaft, and the movable pedal arm has a lever which moves as one therewith. A torsion coil spring is arranged under an initial torsional moment between the free end of the lever and the support bracket. The first end of the sping is rotatably supported on the bracket, while the second end thereof is secured to the lever. Before the pedal is operated, the second end of the spring is located on the pedal-return side of a segment which connects the center of the support shaft and the first end of the spring.
Thus, in the case of the apparatus with the aforementioned construction, when the pedal arm is pushed in by being trod on, the repulsive force generated the spring urges the pedal arm to return before the second end of the spring reaches the segment connecting the center of the support shaft and the first end. However, when the pedal arm moves to a position such that the second end passes the connecting segment, the repulsive force of the spring then begins urging the arm to move in the direction in which it is being pushed. As a result, the effort required to operate the pedal can be reduced.
If, in the prior art apparatus described above, a torsion coil spring having a larger spring constant or a longer lever is used so as to reduce the pedal effort, then the repulsive force generated by the spring acting on the pedal arm is correspondingly increased, with the result that the effort required in the initial stage of pedal operation is greater. Thus, the prior art pedal cannot, initially at least, be operated with ease.